Various types of in-tank or in-line fuel pumps are used for pumping fuel from the fuel tank to the engine of an automobile. One distinguishing feature among fuel pumps is the type of pumping mechanism employed. For example, gerotors, roller vanes, and regenerative turbines are common due to their compactness and ability to generate relatively high pressures, in the range of 3.5 psi to 150 psi (20 kpa to 1035 kpa). Since these pumps must rotate at high speeds to achieve the desired flowrate and pressure, cavitation may occur, resulting in a host of fuel handling problems, including fuel vapor within the fuel, hot fuel, noise and decreased pump efficiency. In order to minimize these drawbacks, the pumps must be designed to include compensating features such as vapor purge orifices, vapor purge channels, modified regenerative turbine impellers, and dual stage designs with the positive displacement stage acting at higher pressure heads. These additional features increase manufacturing costs and may complicate assembly.
A contributing factor to the abovementioned problems with conventional pumping mechanisms is the relatively short distance over which the fuel pressure is increased. For example, fuel pumped through a regenerative turbine (FIG. 13a) or gerotor (FIG. 13b) typically increases in pressure from about 0 psi to nearly 60 psi over approximately a short distance, perhaps one (1) centimeter, which is the circumferential length around the pumping element. This small distance results from size limitations on the fuel pump in addition to the physical construction required for such pumps. The present invention increases fuel pressure over a longer circumferential distance (FIG. 13c) thus decreasing cavitation and increasing pump efficiency.
Another drawback of regenerative turbines and gerotors is that they are typically housed in a pumping chamber formed by a cover and a bottom. The pumping chamber is then mounted within the fuel pump and fuel is drawn through an inlet in the cover, pumped around the pumping chamber, and sent through an outlet in the pump bottom leading to the interior of the pump casing. The need for this pump housing (cover and bottom) within the fuel pump increases manufacturing and assembly costs.
The present invention provides a helically shaped rotary pumping element which does not require a separate pump housing within the fuel pump, thus eliminating the need for a cover and bottom as described above. The present invention also increases fuel pressure over a longer distance than conventional pumping elements, thus reducing cavitation and problems attendant thereto, and increases pump versatility by facilitating design changes to the impeller inlet area, number of helical turns, speed, helical blade angle, and leading edge tip design.